Apr 26, 2015

Rotate It! Bed Position Matters in 3D Printing

Getting my 3D Prints to stick to the bed is probably one of my biggest challenges. It's mostly with small parts - and I've mostly had issues when trying to print many copies of the same part all at once. But recently, there was a specific part which was giving me issues where a little experiment uncovered something surprising.

The Problem

The part I was printing is a link for a bracelet - so it is only about 25mm square and has 4 protrusions starting at the base layer which are the receptacles for pins which hold each link of the bracelet to the next. Those protrusions - or two of them in particular - were peeling up from the bed after the first few layers of printing, and causing the printer extruder head to force it out of the way as it printed successive layers. This caused some mis-shaping - but luckily the model would eventually self-correct and continue printing to the end without forcing the whole object to come loose from the bed. You can see the start of the problem pretty clearly in the video embedded here - the protrusions on the right side are fine, but not on the left - notice how they are higher than the current print layer.
The ultimate impact of the peeling was that the protruding parts where the peeling occurred were mis-shaped and not smooth at all in the final object. The print head eventually re-melted and flatted the problem sections, but not in the way which the part was supposed to be printed. You can see this in the images here too.
Here's a close up of the final print - those protrusions which had the problems (now shown on the right) were consistently mis-shaped.
Original Position - the left protrusions were the ones experiencing peeling
For you technical 3D Printers - this is the bottom layer from CURA - in the original rotation position

Discovery of an Idea

I was using  a live video service - Periscope, on twitter (@periscopeco) - to show people this particular print, and someone commented that perhaps it was the position of the object's receptacle parts that was making this worse. I figured it was worth a simple experiment - since I had tried a few other fixes that didn't help.

Experiment - Rotate the Object

Without changing the model or the slicing parameters at all, I rotated the part 90 degrees clockwise so that the receptacle which had the worst effect was now not the first part of the print layer. I could tell right away that this small adjustment did have an impact, as the first few layers of printing were clean and flat, and there was no peeling off the bed. In the prior experiment, I had slowed the printing of the bottom layer to 15mm/sec (in advanced settings in CURA) - but that adjustment alone did not help - but I left it like that and did the rotation.

After 90 degree rotation, the receptacles are now printing smoothly and are shaped as expected in the model design.
NEW ROTATION POSITION, with the problem parts now pointing away from me on the print bed.

And again for the technical folks, the bottom layer shows hardly any pattern change - just the rotated position.


In the end, the object printed much better, without peeling, with a simple 90 degree rotation! I was quite surprised - but pleased of course. Now I am analyzing the layers to see what may have changed in the slicing - so that I can get to the bottom of what the rotation changed in the printing commands, as I have a hard time believing that the rotation itself actually matters. But - TRY STUFF! When you have a problem, try lots of potential changes to the printing parameters and even the positioning on the bed. You never know what you might discover.

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